Various communication networks manage traffic routing, including recovery from route failure. For example, a network may comprise a centralized element or run a routing protocol that re-routes the traffic of a failing route via an alternative path. Methods for re-routing upon failure are known in the art.
For example, U.S. Patent Application Publication 2011/0249679, whose disclosure is incorporated herein by reference, describes a method for implementing fast re-route (FRR) by starting up an upper layer software protocol to manage and configure a FRR route. The upper layer software protocol sends down an active next hop of the FRR and a driver writes an IP address of the FRR into an ECMP table and creating a software table to record correspondence between a FRR group and an ECMP group. The upper layer software protocol informs the driver of a prefix address of a subnet route and the index of the FRR group. The driver finds the index of the ECMP group, and writes information of the subnet route and the index of the ECMP group into hardware. The upper layer software protocol informs the driver of the index of the FRR and an IP address of a new standby next hop. The driver looks up for the index of the ECMP group, and updates the next hop address of the ECMP group.
As another example, U.S. Pat. No. 7,234,001, whose disclosure is incorporated herein by reference, describes a method and apparatus that provide protection against resource failures in Open Shortest Path First (OSPF) networks. An internal router (IR) automatically maintains a back-up link in a dormant state until a network failure affecting communications with a primary adjacent area border router (ABR) is detected. Upon detection of the network failure, the IR activates the back-up link in order to enable traffic flow to an alternate adjacent ABR, which by-passes the network failure. Upon recovery of communications with the primary adjacent ABR, the IR automatically deactivates the back-up link and resumes traffic flow through the primary adjacent ABR.
As yet another example, in “Network Architecture for Joint Failure Recovery and Traffic Engineering,” whose disclosure is incorporated herein by reference, Suchara et al. describe a unified way to balance traffic load efficiently under a wide range of failure scenarios. The proposed architecture supports flexible splitting of traffic over multiple precomputed paths, with efficient path-level failure detection and automatic load balancing over the remaining paths. The authors propose two candidate solutions that differ in how the routers re-balance the load after a failure, leading to a trade-off between router complexity and load-balancing performance.